Computer applications that utilize touch screens for communication between the program running on the computer and the user are increasingly commonplace. As a result, electronic instruments are migrating toward the use of touch screens for mediating the interaction between the user and the control of the instrument. In particular, touch screens are being used in oscilloscopes. Oscilloscopes, however, present unique problems when gestures are used to select and manipulate waveforms on the screen.
On prior art oscilloscopes, a user selects a waveform on the screen by touching the waveform. The oscilloscope display, however, differs from a tablet or similar touch screen enabled device in that the oscilloscope display can have a number of overlapping waveforms that are displayed simultaneously. Typically, the oscilloscope displays waveforms from a plurality of channels simultaneously. These waveforms often overlap. Hence, to select a particular waveform by touching the screen, the user must find a place on the screen in which that waveform is isolated from the other waveforms by an amount that allows the user to touch that trace without the user's finger touching another trace on the screen. Finding an appropriately isolated area presents challenges in many cases. Hence, the computer program often selects the wrong trace. In this regard, it should be noted that the touch area on the screen is an area the size of the user's fingertip. Hence, even though two waveforms appear to be separated on the screen, the user actually touches both waveforms. The computer program typically selects one of the waveforms, which in many cases is the wrong waveform.
In addition, users often regard the area around a waveform as being part of that waveform. For example, users often regard the area under a pulse as being part of the waveform. Hence, the user tries to select the pulse waveform by touching the screen in the area under the peak of the pulse. However, the computer program does not recognize this area as part of the waveform, and hence, no waveform is selected.
Oscilloscope displays also differ from conventional tablets and similar devices in that the gestures being performed on the screen are directed to a single waveform, rather than the displayed image as a whole. For example, a “pinch” gesture on a tablet is normally used to zoom in or zoom out on the scene being displayed. That is, the gesture is used to change the magnification of the scene. On an oscilloscope, the user usually wishes to change the gain or time scale of a single trace, while leaving the gain or time scale of the other traces unchanged.